Apparatus for perforating acoustical plaster ceilings



Dec. 29, 1964 c. M. BLACKMON 3,163,064

APPARATUS FOR PERFORATING ACOUSTICAL PLASTER CEILINGS Filed July 3, 1961 INVENTOR. CHARLES M. BLACKMON 64 1 W maw ATTORNEYS.

United States Patent 3,163,064 APPARATUS FOR PERFORATING ACOUSTICAL PLASTER CEILINGS Charles M. Blackmon, 1312 30th St. NW., Washington, D.C. Filed July 3, 1961, Ser. No. 121,661 9 Claims. (Cl. 83-1) This invention relates to an apparatus for perforating acoustical plaster ceilings and more particularly for use on an acoustical plaster ceiling which has been coated one or more times and has lost the original acoustic properties.

At increased expense, many builders have provided ceilings having an outer surface formed of acoustical plaster, that is a plaster having high sound-absorbing properties. In the original construction of ofiice buildings, or the like, it is necessary to reduce the general noise level to a point where it is not objectionable. After occupancy for a number of years, to renew the general appearance, the office buildings normally have their interiors repainted. In cases where the acoustical plaster ceiling is repainted, the paint in covering the plaster causes the plaster to lose its acoustic absorption properties and while the net result is to provide a more habitable and generally pleasing surroundings, sound absorption is lost.

It is therefore a primary object of this invention to provide an apparatus for restoring the sound absorption capability to an acoustical plaster ceiling which has been coated or painted to the extent that the ceiling has lost these properties.

It is a further object of the invention to provide an apparatus which may be conveniently operated by a single person in restoring .the sound absorption capabilities to a coated acoustical plaster ceiling.

It is a further object of this invention to provide an apparatus of this type in which the means for restoring the sound absorption capability of the acoustical plaster ceiling is adjustable for ceilings of various heights and in which the force exerted by the restoring element as it is moved across the ceiling may be varied to provide maximum restoring action with negligible damage to the plaster ceiling.

Other objects of this invention will be pointed out in the following detailed description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of this invention in the best mode which is contemplated in applying that principle.

In the drawings:

FIGURE 1 is a perspective view of the apparatus forming the preferred embodiment of this invention;

FIGURE 2 is a partial view of the roller forming a portion of the apparatus of FIGURE 1 showing the specific configuration of the perforator studs projecting from the surface of the roller; 7

FIGURE 3 is a partial view of a portion of the roller forming a part of the apparatus shown in FIGURE 1 illustrating an alternative configuration for perforator studs forming an element thereof.

In general, the apparatus of this invention consists of means for restoring the sound-absorbing capacity to a coatedacoustical plaster ceiling and consists of a rotatable element adapted to frictionally engage the surface of the acoustical plaster ceiling with perforating means car- .ried on the outer surface of the element for penetrating the outer coating and the major thickness of the acoustical plaster ceiling to expose a plurality of spaced,. raw plaster surfaces throughout the ceiling area. Means are provided to cause the perforation means to enter the plaster as the rotatable element is moved across the ceiling under sufiicient pressure to cause penetration of ice the coating and the acoustical plaster to renew the acoustic receptivity of the ceiling. In one form the apparatus of this invention is provided with a platform mounted on dolly wheels and adapted to be moved across the floor of the building by a single operator. The platform includes a vertical support member carrying a pivotable extension arm to which is attached at the free end thereof, a cylindrical roller carrying randomly spaced perforator studs. The pivotable extension member is flexible enough to allow the cylinder to contact the ceiling with a variable force set up by an adjusting member coupled to the extension arm and variably positioned by the operator to both vary the angular position of the extension member and the force exerted on the roller tending to move it into contact with the ceiling.

Referring to the drawings, there is shown the apparatus in the present invention in a preferred form, comprising a generally rectangular base or platform 10 which includes at the forward end a pair of fixed casters 12 having wheels of suitable diameter such as 8 inches and at the rear a like pair of spaced pivotable casters 14 allowing the platform 10 to be moved over a floor surface with great maneuverability. A main frame member 16 consisting of a pair of vertical spaced tubular members 18 is rigidly fixed to the upper surface of platform ill and includes a number of transverse connecting rods (not shown) which act to rigidity the structure while at the same time give enough support to allowthe operator to use this portion of the apparatus as a ladder to make adjustments, etc. A second vertical support member 26 including bars 22 is rigidly mounted on platform 1% forward of support member 16, the bars 22 are inclined slightly in a rearward direction and are rigidly coupled intermediate their ends to the vertical support member 16 by cross bars 24, the upper ends 25 of the vertical support bars 22 extending beyond the ends of the support member 16. A third pair of vertical supportmembers 26 are positioned near the front of the platform 10 and are rigidly coupled at the bottom end to the platform and at the upper end to the support member 20 above the point where support members 16 and 20 are joined. This in effect provides an extremely rigid support for a pivotable extension member generally shown at 28 which is pivotally connected to the upper end 25 of support member 26 by a transverse rod 3%. The sides of the extension member 28 may be hollow to allow a pair of supporting rods 34 to be positioned therein, the rods 34 being somewhat flexible so as to provide resiliency and act as biasing means for biasing a perforator roll 36 against the ceiling surface. The perforating means 36 consists of an elongated cylindrical roll 37 v preferably 6 to 8 inches in diameter having a relatively perforator roll 36.

smooth surface except for the placement of a plurality of spaced perforating studs 39 which extend normally from the surface thereof for causing perforations to be formed in the coated acoustical plaster in a manner hereinafter described. A transverse rod 40 connects the two rods 34 and acts as a support axis for the rotatable It is apparent therefore that the basic apparatus of this invention consists of means for moving a perforator roll 36 against :the ceiling surface and thereupon moving the platform 10 to cause the roll to frictionally engage the surface and rotate about its axis to cause the perforating studs 39 to perforate the ceiling surface as the platform 10 is manually moved across the floor of the room. In order to propel the platform It) a pair of upstanding support members 44 are provided at the forward end of the platform 10 with a horizontal connecting bar 46 acting to supply sufficient suppont for a transverse handle'or arm 48. The operator merely pushes on the handle 43 and may thus propel the platform 10 across the room in a desired direction.

Of particular importance to the present invention, is the means for adjusting the vertical height of the roller axis it! to allow the apparatus to be used with rooms of various ceiling height, and at the same time to provide means for varying the pressure exerted by the perforator roller 36on-the acoustical tile ceiling. This is extremely important since. the usual depth of acoustic plaster is approximately to' 7 of an inch. In the passage of the perforator roller 36 over the surface of a ceiling, the pressure that is required is that which will result in penetration of the paint or other coating and the acoustical plaster itself. The penetration provides a sound absorption pattern of randomly spaced holes which are deep enough to expose a certain amount of raw plaster surface to allow the raw plaster surface to absorb the sound sufficiently to reduce the noise level to a point where it is not objectionable. The particular roller configuration and the configuration of the perforator studs is extremely important to the efiicient operation of this machine and will be described hereinafter. It i important to note at this time-that the normal acoustic plastered ceiling includes a base formed of corrugated metal laths upon which is provided a brown coat which is a. plaster having a hardness as much as five times that of the outer coating of acoustical plaster which is normally /4 to 3/3 inch in depth. Since it is important only to erforate the acoustic plaster and, of course, provide areas of raw acoustic plaster which may absorb the sound, the depth of the perforation is extremely important. It has been found that if the perforator studs are made too long, they will contact and actually crack the brown plaster coating, especially if an abnormally iarge force is exerted on the perforator roller as it is moved across the ceiling.

In order to provide means for rotating the extension member 28 about the pivot point provided by transverse rod 30, a vertical adjusting member 52 comprising a pair of spaced vertical rods 54 and a series of transverse connecting rods (not shown) is pivotally attached to the extension member 28 intermediate its ends by means of transverse support shaft 58. It is apparent therefore that vertical movement of member 52 will cause an extension member 28 to rotate about shaft 30 to move the roller 36 toward the ceiling surface. In order to regulate the height of the cylinder 36 and to vary the pressure exerted against the ceiling surface by the cylinder, a suitable hand-positioned adjusting lever is provided. At the lower end of the vertical height adjusting member 52, there is provided a number of inwardly extending spacedpins 56 which are rigidly coupled to the side members 54 facing each other. The pins 56 are of relatively short length, and are adapted to receive the ends of a U-shaped adjusting arm 62, the arm 62 being formed from a pair of sheet metal L-shaped frames 69 which are joined centrally to a rearwardly directed horizontal adjusting armor lever 64 which extends past one of the vertical support members 44. A pair of spaced bushings 66 are mounted for rotation on a transverse support member 68, each of the bushing members including a downwardly projecting arm 70 which is attached to its associated L-shaped frame member 60, intermediate of adjustingleve-r 64 and the terminal portions 58 of the U-shaped member. Support rod 68 is vertically adjustable by use of bushings 69 mounted on rods 18. Suitable holes '74 are formed within terminal portion 58 and the holes 74 act to receive the pins 56 to provide means for varying the location of the connection between the horizontal adjusting lever 64 and the vertical adjusting member 52. At the forward end of the apparatus adjacent the handle 48, there is provided a series of latching means 76 which may take the forms of lateral projections or notches cut into the vertical support member 44. The adjusting arm pivots about bushings 66 with the adjusting lever 64 being adjustably locked at various heights in order to define both the height of the perfoplaster and in some cases cracks.

rator roller 36 and the amount of force with which the roller 36 contacts the ceiling.

Prior to the operation of the perforator apparatus, the operator judges the apparent height of the ceiling and makes adjustments such that the roller 36 will not only contact the ceiling, but with a desired pressure, this pressure being generally constant as the machine is moved across the floor. It is readily apparent that extension rods 34 may be either relatively short or relatively long in length depending upon whether the room has an 8 foot ceiling, a 12 foot ceiling, or greater. It may be only necessary to provide a choice of two rod lengths for rods 34 since intermediate adjustments may be made through the use of the remaining portion of the apparatus. In this regard, the operator after placing the desired rod length 34 within the extension member 28, may position the U-shaped yoke member 62 on a suitable pair of pins 56, such that vertical movement of the adjusting lever 64 will then result in vertical movement of the perforator roll 345 with respect to the ceiling. Once the ceiling has been contacted, continued downward movement of lever 64 Wiil result in no further vertical movement of the perforator roll 36, but will result in additional pressure being exerted by this roil against the ceiling which will cause the rods 34 to flex. It should be noted that the position of the pivot point about rod 68 will create quite a mechanical advantage since the distance between this rod and the operating portion 78 is much greater than the distance between rod 68 and the connecting pins 56 on the vertical height adjusting member 52.

Since the purpose of the perforations is to provide an area of exposed raw acoustic material and thus restore in a large measure the original acoustic quality of the ceiling plaster which was lost as a result of having been painted, it is important that the perforating roller 36 provides for each individual perforation a maximum zone of acoustic receptivity with respect to the actual area formed by the perforation within the plaster. Referring to FIGURES 2 and 3, it is to be noted that the perforator studs 39 on the perforator roller 36 are approximately /4 of an inch in length so that the passage of the perforator roller over a ceiling, in using the necessary pressure, will result in the penetration of the painted coating as well as the major depth of the acoustic plaster layer itself. This will provide a sound absorption attern deep enough to absorb sound or noise sufficiently. The studs may be placed randomly or a definite pattern may be provided. It has been found that the configuration of the perforator stud is extremely important to the formation of the maximum zone of acoustic receptivity within each perforation. For instance, it was found that a stud having a simple conical configuration would provide a minimum area of raw acoustic material since the penetration of the cutting or punching element of this type would result merely in the compression of a material adjacent the area and actual failure to provide a zone or wall surface of raw acoustic material. While a punch having a generally cylindrical configuration would result in the paint being pushed to the bottom of the hole, and thus the exposure of an acoustic working zone comprising a cylinder of raw acoustic material, the use of a punch of this configuration resulted in extensive damage to the The ideal stud configuration resides in the formation of a three or four sided truncated pyramid at the forward end or point of the stud member. Thus, in FIGURE 2, each of the stud members 39 comprises a cylindrical base indicated at which may be originally secured in suitable perforations 192 formed in the surface of the hollow cylindrical roller 36. The outer ends of the studs are tapered to form four inclined surfaces lit!- and an outer flat rectangular contact face 106 in the form of a truncated pyramid. Alternatively as shown in FIGURE 3, the stud is shown to have a cylindrical base 116, three tapered terminal sections 112 and a triangular contact face 114 which also forms a three-sided truncated pyramid adjacent the outer end of cylindrical portion 110.

The perforator-roller 36 may be formed in various widths, an 18 inch roller for instance for general use, while a 6 inch roller may be provided to cover small strips such as between light fixtures or where there is an edge left after using the large roller which is too narrow for the 18 inch roller. As mentioned previously, the diameter of the perforator roller is preferably in the order of 8 inches which has been found to be the most efilcient size to deliver cleanly cut punched holes of a depth of A of an inch. The depth of the hole can be increased by increasing the stud length, although it is not necessary to do so to obtain the desired acoustic result. The actual diameter of the individual holes can also be varied, but the size selected is approximately of an inch. If the hole is made too small in diameter, it may be eventually closed by repeated coats of paint and of course the plaster would again lose its acoustical quality. A random pattern was selected since it minimizes the possibility of the plaster clinging to the perforator roller as it moves over the surface of the ceiling under pressure. The random pattern also permits the operator to cover a ceiling rapidly because he does not have to rigidly and slowly follow a line or carefully keep his machine in line as would the case be if the pattern selected used rows of holes in lines. In the operation of the machine, the operator makes suitable adjustment by varying the vertical position of the bushing members 69 and transverse rod 68 on the vertical support member 16, the placement of the yoke member 62 on the pins 56 and the selection of the roller support rods 34, such that the perforator roller is positioned adjacent the ceiling. The operator then brings the perforator mller into contact with the ceiling and slowly jacks it by lowering the adjusting lever 64 until the studs 39 have penetrated to their complete depth into the plaster. He then locks the adjustor handle 78 into position against one of the latching members 76 and manually pushes the machine from one end of the room to the other. The operation may be performed by first forming two outside perforated strips along the outside of the walls of the ceiling on the outside edges of the ceiling in line with the baseboard. Perforating may be then continued over the ceiling by aligning the perforator roller with the edge of the preceding perforated strip. The perforator roller has a guard (not shown) attached to it to prevent the perforating studs from striking the side walls at the end of the room. It is only necessary when the operator reaches the end of the room to release the adjusting lever 64 from its locked position and lower the perforator roller sufiiciently to clear the ceiling, turn the machine around and make another run. Having noted the position of the adjusting lever 64 with respect to the locking means 76, the operator returns it to the same position and immediately proceeds to push the machinein the opposite direction. The transverse rods actually form a built-in ladder to enable the operator to quickly check the functioning of the perforator roller and to make certain that it is penetrating to the full depth of the perforator studs.

In the present invention, it is obvious the device may be used to perforate an acoustical plaster which is painted and therefore no longer possesses acoustical properties. The machine is so designed that the pressure on the perforator roller can be increased and decreased, with the pressure being adjusted to the amount necessary for the perforator roller to penetrate the painted acoustical plaster the full depth of the studs. Since this pressure is considerably less than that required to penetrate the underlying hard foundation plaster known as the brown coat, the use of the present invention will insure that only a desired pressure may be provided so as to completely penetrate the acoustic plaster without in any way afiecting the base material. It is to be noted that the speed of perforation of an acoustic plaster ceiling which has been painted over is greatly in excess of the time required to apply perforated tiles. Advantages of this machine are obvious since at relatively low cost, the acoustic properties of an acoustic plaster ceiling may be restored in large measure where the original acoustic qualities of the plaster ceiling has been lost as a result of having been coated by paint or other materials. In addition, in newly constructed buildings in which the 'final layer of plaster on the ceiling is of the nonperforated acoustic type, it may be desirable to use the machine of the present application in the manner set forth above to perforate the acoustic plaster layer and provide a pleasing perforated appearance, while at the same time exposing increased surface areas of raw acoustic material to further enhance the acoustic receptivity of the acoustic plaster ceiling. While the apparatus of the present invention is specifically directed to the need for restoring the sound-absorbing capacity to a coated acoustic plaster ceiling, the present invention is intended to fully encompass like operation to a new acoustic plaster ceiling.

While there have been shown and described and pointed out the fundamental novel features of the inven tion as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. Apparatus for restoring the sound absorbing capacity to a plaster ceiling including an outer, coated, acoustic plaster layer comprising: a rotatable element adapted to frictionally engage the surface of said ceiling and rotate thereon, perforating means carried by said element and adapted'to penetrate the surface of said coated acoustic plaster layer to expose an area of raw acoustic material, mechanically adjustable means for forcing said element against said ceiling, means for resiliently biasing said element against said ceiling to cause said perforating means only to enter said plaster, and means for moving said rotatable element across said ceiling under pressure to renew the acoustic receptivity of said acoustic plaster layer.

2. Apparatus as claimed in claim 1 wherein said perforating means comprises a plurality of perforating, randomly spaced studs positioned normal to the surface of said rotatable element. the studs being of a height approximately equal to the thickness of said coated acoustic plaster, each of said studs including means for forcing said coating material to the rear of said perforation within said acoustical plaster to expose an area of raw acoustic material within said perforation.

3. Apparatus as claimed in claim 1 wherein said perforating means comprise a plurality of studs extending radially from said rotatable element, said studs having a free radial length in the order of the thickness of said coated acoustic plaster layer and including a base portion of constant width and a tapered terminal portion to force said coating material to the rear of said perforation within said acoustical plaster layer to expose an area of raw acoustic material within said perforation.

4. Apparatus as claimed in claim 1 wherein said perforating means comprise a plurality of perforating studs positioned normal to the surface of said rotatable element, the studs being of a height approximately equal to the thickness of said coated acoustic plaster layer with each of said studs including a base portion and a tapered terminal portion with said base portion having a thickness at the point where said base portion joins said rotatable element which is not less than the thickness of said base portion at the point where said base portion joins said tapered terminal portion.

5. Apparatus for restoring the sound absorbing capacareases ity to a plaster ceiling including an outer, coated, acoustic plaster layer comprising a horizontal base member adapted to move across the floor, a stationary first ver tical support member fixed to said base, a second vertical support member movably mounted on said first vertical support member, a rotatable element, means for resiliently supporting said rotatable element on the end of said movable support member, perforating means carried by said rotatable element and means for variably positioning said movable vertical support member with respect to said stationary vertical support member for varying the vertical height of said rotatable element and increasing the bias of said resilient means to cause said perforating means to enter said coated plaster layer whereby movement of said horizontal base member across the floor causes penetration of said acoustic plaster and renewal of the acoustic receptivity of said acoustic plaster ceiling.

6. Apparat-us for restoring the sound absorbing capacity to a coated acoustical plaster ceiling comprising a horizontal base member including means allowing movemerit of said base member across the floor of a room, a stationary vertical support member rigidly attached to the upper surface of said horizontal base member, an extension member pivotally attached to the upper end of said vertical support member and adapted to rotate in an arc toward and away from said ceiling, a rotatable element carried by the free end of said extension member, a vertical adjusting member pivotally connected to said extension member at a point spaced from said pivot point between said extension member and said fixed vertical support member, said rotatable element including perforation means adapted to contact the ceiling, and means for adjusting the vertical height of said vertical adjusting member to cause said roller to move toward and away from said ceiling, whereby said perforation means enter said plaster to renew the acoustic receptivity of said acoustic plaster ceiling.

7. Apparatus as claimed in claim 6 wherein said means for adjusting the height of said vertical adjusting member includes a horizontal adjusting lever, said adjusting lever being pivotally connected at one end to said vertical adjusting member and extending past said fixed vertical support member generally at right angles thereto, means for pivotally connecting said horizontal adjusting lever to said fixed vertical support member at a point spaced from said pivotable connection between said lever and said vertical height adjusting whereby vertical depression of the free end of said adjusting lever causes said perforation means to move into contact with said acoustical ceiling.

8. Apparatus as claimed in claim 7 including means for locking said free end of said adjusting lever in one of several vertical positions to vary the height of said perforator roller and the pressure exerted by said roller on said acoustical plaster ceiling.

9. Apparatus as claimed in claim 7 including second vertical support means fixedly attached to the upper surface of said movable platform including a series of spaced latching means, said latching means acting to receive the free end of said adjusting lever to variably position the height of said perforator roller and the pressure exerted by said roller against said acoustic ceiling.

References (Zited by the Examiner UNITED STATES PATENTS 424,676 4/90 Jensik et al. 30-365 515,633 2/94 Warth 30365 580,287 4/97 Marsh 3()365 1,922,248 8/33 Kelly 837 2,205,731 6/40 Olsen 83--1 2,234,789 3/41 Wunderlich l44-ll0l1 2,435,349 2/48 Hall 3G365 FOREIGN PATENTS 523,102 7/40 Great Britain.

ANDREW R. IUHASZ, Primary Examiner.

EDWARD V. BENHAM, HUNTER C. BOURNE, JR.,

Examiners. 

1. APPARATUS FOR RESTORING THE SOUND ABSORBING CAPACITY TO A PLASTER CEILING INCLUDING AN OUTER, COATED, ACOUSTIC PLASTER LAYER COMPRISING: A ROTATABLE ELEMENT ADAPTED TO FRICTIONALLY ENGAGE THE SURFACE OF SAID CEILING AND ROTATE THEREON, PERFORATING MEANS CARRIED BY SAID ELEMENT AND ADAPTED TO PENETRATE THE SURFACE OF SAID COATED ACOUSTIC PLASTER LAYER TO EXPOSE AN AREA OF RAW ACOUSTIC MATERIAL, MECHANICALLY ADJUSTABLE MEANS FOR FORCING SAID ELEMENT AGAINST SAID CEILING, MEANS FOR RESILIENTLY BIASING SAID ELEMENT AGAINST SAID CEILING TO CAUSE SAID PERFORATING MEANS ONLY TO ENTER SAID PLASTER, AND MEANS FOR MOVING SAID ROTATABLE ELEMENT ACROSS SAID CEILING UNDER PRESSURE TO RENEW THE ACOUSTIC RECEPTIVITY OF SAID ACOUSTIC PLASTER LAYER. 